The present invention relates to a medical X-ray CT (Computed Tomography) apparatus or an image display apparatus and an X-ray CT apparatus each of which realizes an improvement in image quality of a three-dimensional image display image comprised of a continuous tomographic image at a conventional scan (called also “axial scan”), a cine scan, a helical scan, a variable-pitch helical scan, or a helical shuttle scan executed in an industrial X-ray CT apparatus.
An MPR (Multi Plane Reformat) display corresponding to one of three-dimensional image display methods has heretofore been effected on a tomographic image continuous in a z-direction corresponding to a table travel direction of an X-ray CT apparatus using a multi-row X-ray detector or an X-ray CT apparatus using a two-dimensional X-ray area detector of a matrix structure typified by a flat panel and an MPR display of an xz plane or an xy plane has been performed as shown in FIG. 15. In this case, a problem arises in that although effects such as an S/N improvement in the xy plane, a reduction in artifact, etc. are brought about when a z-direction adaptive image filter is applied or effected on a tomographic image of the xy plane, spatial resolution is degraded in the z direction and image quality is degraded with respect to an MPR display image of the xz plane or yz.
However, in the X-ray CT apparatus having the multi-row X-ray detector or the X-ray CT apparatus having the two-dimensional X-ray area detector typified by the flat panel, a sheet of tomographic image becomes thin as the cone angle of an X-ray cone beam becomes larger and each detector channel becomes smaller. There is a tendency that S/N of the tomographic image becomes poor on the condition that X ray dosage is constant. However, the X-ray dosage cannot be increased in terms of X-ray exposure of the subject. Therefore, the S/N of each pixel of the thin tomographic image is improved and an adaptive image filter that does not degrade its spatial resolution is determined. On the other hand, each pixel might be observed from various directions of the xy plane, yz plane and xz plane upon the MPR display corresponding to one of the three-dimensional pixel displays. Therefore, when the adaptive image filter is applied in a given fixed direction, degradation of spatial resolution will appear on any of the xy plane, yz plane and xz plane.
Therefore, there is a demand for an adaptive image filter that changes the direction in which it is dynamically applied, following dynamic changes in display and sightline directions. At this time, the adaptive image filter may dynamically be applied in real time upon display.